Tuesday, 30 January 2024: 9:45 AM
323 (The Baltimore Convention Center)
The Jason and Sentinel-6 series satellites use radar altimeters to measure the ocean surface for
monitoring global sea level rise as well as operational observations of regional mesoscale ocean
processes. Radar altimeters emit microwave signals and records the signal traveling time in the
atmosphere to/from sea surface. The signal path delay due to moisture in the atmosphere has large
spatial and temporal variability, and hence can introduce one of the largest uncertainties in the sea level
measurement if not properly accounted for. Nearly all radar altimeter satellites have on-board passive
microwave radiometers measuring the atmosphere water vapor to estimate a wet tropospheric
correction (WTC). With the advanced microwave radiometer (AMR) onboard, Jason-3 has a design goal
to achieve a stability of zero bias and a standard error of 1mm in any year period for sea level. The
Jason-3 AMR onboard calibration design is prone to experience long term brightness temperature drift,
which is corrected with the cold space calibrations through frequent satellite maneuver and vicarious
calibration targets to achieve long term stability. Monitoring stability of the AMR and the WTC retrieval
is a critical step for accurate determination of global sea level rise trend, and further achieving climate
data record quality in the AMR-derived water vapor products.
NOAA STAR operationally ingests and homogenizes global seal level measurements and auxiliary
geophysical parameters from all the altimeter missions into a database, Radar Altimeter Database
System (RADS). Higher level datasets derived from RADS are provided to users for weather/hurricane
forecasting, data assimilation, and climate monitoring. In this study, with current data in RADS, the
Jason-3 AMR stability is monitored and assessed over 7 years period through different vicarious
calibration means, including inter-comparison with JPSS SNPP Advanced Technology Microwave Sounder
(ATMS) over Simultaneous Nadir Overpass, time series analysis at Amazon rainforest, and coldest ocean,
band ratio, as well as global mean methods. Overall, the water vapor band (23.8GHz) and surface
roughness band (18.7GHz) are very stable and cloud liquid band (34 GHz) shows a decreasing trend. All
the trend, stability, standard errors of brightness temperature, in terms of monthly anomaly, are
analyzed and discussed.
monitoring global sea level rise as well as operational observations of regional mesoscale ocean
processes. Radar altimeters emit microwave signals and records the signal traveling time in the
atmosphere to/from sea surface. The signal path delay due to moisture in the atmosphere has large
spatial and temporal variability, and hence can introduce one of the largest uncertainties in the sea level
measurement if not properly accounted for. Nearly all radar altimeter satellites have on-board passive
microwave radiometers measuring the atmosphere water vapor to estimate a wet tropospheric
correction (WTC). With the advanced microwave radiometer (AMR) onboard, Jason-3 has a design goal
to achieve a stability of zero bias and a standard error of 1mm in any year period for sea level. The
Jason-3 AMR onboard calibration design is prone to experience long term brightness temperature drift,
which is corrected with the cold space calibrations through frequent satellite maneuver and vicarious
calibration targets to achieve long term stability. Monitoring stability of the AMR and the WTC retrieval
is a critical step for accurate determination of global sea level rise trend, and further achieving climate
data record quality in the AMR-derived water vapor products.
NOAA STAR operationally ingests and homogenizes global seal level measurements and auxiliary
geophysical parameters from all the altimeter missions into a database, Radar Altimeter Database
System (RADS). Higher level datasets derived from RADS are provided to users for weather/hurricane
forecasting, data assimilation, and climate monitoring. In this study, with current data in RADS, the
Jason-3 AMR stability is monitored and assessed over 7 years period through different vicarious
calibration means, including inter-comparison with JPSS SNPP Advanced Technology Microwave Sounder
(ATMS) over Simultaneous Nadir Overpass, time series analysis at Amazon rainforest, and coldest ocean,
band ratio, as well as global mean methods. Overall, the water vapor band (23.8GHz) and surface
roughness band (18.7GHz) are very stable and cloud liquid band (34 GHz) shows a decreasing trend. All
the trend, stability, standard errors of brightness temperature, in terms of monthly anomaly, are
analyzed and discussed.
In addition, the wet tropospheric correction is retrieved from SNPP ATMS using measurements at 23.8
GHz and 31.4 GHz with an empirical logarithm linear combined equation. The fitting coefficients are
derived between the Jason-3 AMR WTC retrievals and SNPP ATMS brightness temperature over SNOs
over ocean. The derived global WTC monthly anomalies are then compared with WTC retrievals of AMR
and WTC simulations with the ECMWF Reanalysis v5 (ERA5) in RADS for 7 years. The SNPP/ATMS WTC
retrieval with very consistent/stable calibration algorithm provides a new way to validate the WTC
retrievals from different altimeter missions and possible for climate study of atmosphere water vapor
changes.
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